8x50R Aus Forming Issues

I picked up an M95 straight-pull chambered in 8x50R a few months back, and I’m to the point of making brass for it. I have a set of 8x50R dies from RCBS, and have followed the procedure mentioned to make brass from trimmed 7.62x54R brass, but for some reason the rounds (unloaded at this point) won’t chamber without tapping on the bolt handle with a hammer, and I really don’t want to do that.
I will be making a chamber cast this week to confirm the chambering, but the only thing I can think of at the moment is that I’m using Norma brass instead of the PPU that most people are using. Is there a known difference in rim dimensions between PPU and Norma 7.62x54R brass? I did grind down the rim a bit, but it didn’t make much difference (took it down to match the 14.00 mm diameter of my surplus 8x56R rounds I’m using as a rim reference).
Suggestions? Anyone have similar issues with their 8x50R M95?
Attachment 324718

I have one rifle in this chambering and made my brass out of PPU with no issues. The necks were a little long but I found they chambered fine. I would suggest coating one of your cases with a black sharpie then try chambering it, you should get an indication of where it isn't sized properly. My guess would be either the shoulder isn't set back far enough or the base (forward of the rim) is too large. If its not setting the shoulder back enough make sure your sizing die is all the way against the shell holder you should feel it "cam over" on the sizing stroke. If that doesn't take care of it you could turn a little off the base of your sizing die. If the base is too large I would use a lathe and turn the base to fit (you could use a drill and file).

Tom

Maybe a shoulder issue, when I was forming 8x50R brass, I ground ~.010" off the top of a shell holder to use during the initial forming. Using the thinner shell holder allowed the shoulder to be set back a little more, allowing the case to chamber. After first firing the ground shell holder wasn't required.

It's something to try. I formed 8x50R from both 7.62x54R and 8x56R.

I still have a bunch of the formed brass, it shot extremely well out of my buddy's double rifle. Lost him to cancer 9 months ago.

I've considered trying the 8x50R brass in my 8x56R straight pull rifle, don't know how a 6mm shorter neck will work.

Brass is too nice to scrap.

I do have a differently-branded shellholder. I’ll chamber cast, ink my brass, and grind a shell holder to see what difference it makes.

And I prefer grinding down a $5-10 shell holder as opposed to going after a much more expensive sizing die. The dies I used were RCBS and not particularly cheap or easy to come by.

Either method will work, the shell holder is just easier to replace.

I've got a stationary belt/disc sander, it's just a couple of seconds to shorten a shell holder. I've done it to a number of different shell holders over the years.

If you're allowing the press ram to "cam over"....don't. Screw the FL die in further until the shell holder bumps solidly against the bottom of the die w/o the ram or press handle flexing as if wanting to "cam over". Also make sure the decap rod isn't bottoming out on the inside of the case.

I took a chamber cast today and it appears the shoulder of the chamber is about 2mm back from where my reformed cases have their shoulder. Everything else should fit my cases. That being said, putting one of these 7.62x54R cases through the 8x50R die it does not appear that the shoulder moves at all. That explains the shoulder location, which should be about 1.6mm further forward on the Russian case. I’ll be grinding my die down a bit tomorrow and see what results. Lots of work going on this week in various categories...

Grinding did not proceed as planned, but here are some photos of the chamber cast. For reference purposes I’m also going to list the dimensions I’ve found for the 8x50R Austrian case, all in mm:

Overall case length: 50.38mm
Neck length: 6.30mm
Shoulder length: 5.93mm
Body length (including rim): 38.15mm
Rim thickness: 1.38mm
Length with bullet: 76.21mm
Neck diameter: 8.90-9.03mm
Lower shoulder diameter: 12.01mm
Base diameter: 12.48mm
Rim diameter: 14.11mm

From these numbers the distance between the top of the rim and the start of the shoulder should be 36.77mm. Since mine is at 36.93, that’s right about where it should be. The question is: why is everyone else able to chamber 7.62x54R cases when the shoulder of that case starts 38.1mm from the rim? Does my M95 just have a tighter chamber than most? There is a marking on the receiver noting the factory head spacing adjustment, and while I can’t recall exactly what it was at the moment, I recall that there was a significant length of barrel that was called to be trimmed to adjust the headspace when the rifle was new. Any thoughts anyone?

On the up-side the casting confirms what appears to be strong rifling...I want to say 8.30mm groove diameter and 8.14mm lands diameter. Below photos of my chamber cast and of a 7.62x54R case I bought to convert...
Attachment 325035
Attachment 325036

Before you grind on shell holder, is there enough space between bottom of case and shell holder to insert a .010 feeler gauge or feeler stock?
A lot of shell holders have different rim depth space cut into SH.
ymmv

Did some more experimentation and am still puzzled. Can a few fellow members who successfully load for 8x50R (Austrian/Hungarian) measure for me the distance from the top of the rim to the start of the shoulder tapering on their brass that does chamber? It’s either the rifle chamber, the brass, or the dies at this point, and I’m trying to check what others’ dies and chambers are producing.

Wish I still had access to an optical comparator, that is the best way to get the measurement you want. That said I'll try and get a measurement with a digital caliper.

Sos when you colored/dykem/sharpied the case and tried to chamber it like hpbear101 suggest, where was the coloring worn off the case? That will show you where the issue is.

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Originally Posted by hpbear101

My guess would be either the shoulder isn't set back far enough...

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That's my guess.

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Originally Posted by Moleman-

Sos when you colored/dykem/sharpied the case and tried to chamber it like hpbear101 suggest, where was the coloring worn off the case? That will show you where the issue is.

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Finally sharpied both one of my die-formed cases and a dummy 7.62x54R case (both with projectiles and nothing else) and loaded them in. In both cases there is a scrape-ring 1-2mm forward of the start of the shoulder.

So...I'm suspecting the die. Going to send an email to the manufacturer...

Any chance the dies could be for a different 8x50 case like a Lebel? Also if it would help I would be happy to send you a few pieces of my formed brass to compare.

The die cartridge is certain: manufacturer sent them to me directly, they’re stamped, and that manufacturer does not make Lebel dies. I did email them last night, so we will see what their response is. It is possible there was a minor error, as taking my calipers out and removing the decapping pin/expander the shoulder appears to start in the die approximately the distance from the die mouth that it should be from the case rim. That would cause the discrepancy to be exactly the width of a shell holder which is about what I’m seeing. I experimented a little with hammering an unformed case into the empty die but I got the order wrong and messed up the case. For my own notes, my order needs to be: trim case, form with pin to widen neck/mouth, remove pin and use mallet to set shoulder, measure, flare mouth, load projectile, test in chamber...

If that still doesn’t work, yes, the brass for comparison would be appreciated, but let’s see what I can determine with what I have and what the manufacturer says.

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Originally Posted by TheAbe

Finally sharpied both one of my die-formed cases and a dummy 7.62x54R case (both with projectiles and nothing else) and loaded them in. In both cases there is a scrape-ring 1-2mm forward of the start of the shoulder.

So...I'm suspecting the die. Going to send an email to the manufacturer...

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Sounds like the non fireformed cases are hitting where the ring is. I see in your process outline that annealing the necks/shoulders was absent. Often when pushing back a shoulder on a case they will be springy and end up too long for me to chamber unless they're annealed. Still though on some 8x57 cases formed from 270win I was getting this from annealed cases so I trimmed a little (0.010"ish) off my sizer die which fixed the issue. 0.010" isn't much, it's about the thickness of 2.5 sheets of computer paper.

Shame on me for forgetting my basic metallurgy. I was thinking annealing was only useful for preventing case failures, but thank you Moleman for reminding me the elastic modulus and the maximum elastic strain also can increase with prior plastic deformation. Since these are once-fired cases, they’re probably over-worked and only elastically deforming when force is applied in the die at the shoulder (neck stays deformed because the deformation is greater).
Ok I’ll anneal and report back. Hopefully I’ll get a chance to this weekend.

Whelp, the annealing didn’t make a difference with shoulder position. Manufacturer wasn’t much help either: just told me to make sure I had the die seated far enough down, and something about brass flow messing up the headspace if I don’t have the die far enough down. Do they realize this is a rimmed cartridge? Anyway, I need to find someone with a lathe locally to turn down the die about 2mm...

Does unfiered 7.62x54r cartridges fit in the chamber ok?

I was hoping the annealing would do the trick for you. You don't suppose they sent a 8x56R or a 8x50 Lebel die mismarked as a 8x50R do you? Your chamber cast looks like a 8x50R which has more of a shoulder than the 8x56R. I'd be tempted to do a casting of the die to see what the ID of it measures.

I haven’t had the ability to test any, but FL-sized 7.62x54R does not fit...hits the shoulder.

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Originally Posted by Moleman-

I was hoping the annealing would do the trick for you. You don't suppose they sent a 8x56R or a 8x50 Lebel die mismarked as a 8x50R do you? Your chamber cast looks like a 8x50R which has more of a shoulder than the 8x56R. I'd be tempted to do a casting of the die to see what the ID of it measures.

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I don’t believe the manufacturer makes 8x50R-Lebel dies, nor 8x56R dies. My chamber cast does look like an 8x50R vs an 8x56R (and 8x56R won’t chamber anyway...got some “free” with my en-bloc clips).
One other possibility is that at one point, this rifle may have had its barrel removed and re-attached...what would be the result if it were tightened one revolution too much? Would that effectively shorten the chamber 1 thread width? Is that even a possibility? I’ve never removed or attached a barrel before and am uncertain what all goes into the process of head spacing for a rimmed-cartridge rifle barrel... any input from those whom have?

A rimmed cartridge should headspace on the rim, not the shoulder. The chamber can actually be somewhat sloppy from that standpoint as the shoulder just needs to allow the cartridge to chamber. Critical headspace dimension is the rim thickness in relation to the bolt face.

On suggestion of a member I tried taking a formed case, removing the decapping pin, and pressing it back on the die on top of the shell holder. This helped, but a dummy round still won’t quite fully chamber. The case revealed scratches mid-shoulder now. I’m going to try new PPU brass, since that’s what everyone else seems to be having success with, and if that doesn’t work the die is going to be trimmed.

Has anyone else had issues with a new 8x50R die they purchased in the pst few weeks?

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Originally Posted by junkbug

Does unfiered 7.62x54r cartridges fit in the chamber ok?

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Took the dies, casting, and formed cases to my lgs for advice. After a bit of discussion and measuring he gave me a few loose unfired 7.62x54R Winchester brass he had laying around to experiment with. I’m hopeful as the shoulders of these unfired cases seems set back about as much as they need to be. Will Test as soon as I’m able.

Ok, new angle: this is a photo of the chamber as best I could do with my phone. Is that a bit of broken extractor wedged in there? The shiny bit sticking around the rim and back into the cutout for the extractor (upper right in photo depending on orientation.). It doesn’t interfere with the extractor when nothing is in the chamber but if that’s piece isn’t supposed to stick there, I’m thinking that might be smashing against the rim of the cartridges when chambering.
I suspect this because my latest experiments had me pushing back the shoulder of my cases using an 8x50R Lebel sizing die, which has the shoulder back a few mm even from the 8x50R Austrian.

Any suggestions for removing this if it isn’t part of how the chamber is supposed to be shaped?
Attachment 326028

You've probably already tried this, but have you ever thoroughly cleaned out and polished the chamber? Is it at all possible that the chamber of your rifle is either slightly pitted or rusted? A good cleaning with a brass brush chucked to a short cleaning rod and cordless drill might be needed/might be a burr or rusty spot that is inhibiting the chambering of your new cases. There are other posts on the site regarding chamber cleaning/polishing.

I had the same problem using 54R Norma but chucked the sizing die up in my tool room lathe. It fit in a 5C collet. I used a carbide cutter to remove .012" off the face of the die. Worked great! Most rifle sizing dies are case carburized. You can't machine em with a high speed cutting tool. Have to use carbide. Don't forget to put a slight chamfer on the inside face and polish with some emery cloth.

If only I had a lathe....one of those long term life goals. Or maybe I should inquire with my cousin who has a few. Either way, I’ve ordered an adjustable hand reamer of the size range of the rim. Hopefully that’ll suffice to slowly grind out or cut out the obstruction without damaging the chamber.

Some success with a rotary file against the obstructing bit. I can now chamber dummy rounds with a rim diameter under 14.20mm. I’m going to work at it a bit more to ensure I don’t need to grind all my case rims down.

I think I found a solution and what the problem was in the first place, and that is extremely tight headspacing, which on a rimmed cartridge is the thickness of the rim. The solution: grind off the beveled part of the base of the 7.62x54 cases before sizing/forming, or after, it doesn’t really matter. PPU brass has a bit thinner rim to begin with so it’s easier for me to get to the proper point, but both they and the Norma (and the couple of Winchester cases I have) all need to be ground a bit to reliably chamber and they reliably chamber. See below, left case will chamber and is ground, right case will not chamber fully.
Attachment 327509

Does that have any effect on seating depth of primer? Usually you would reduce rim thickness on the forward surface of the rim.

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Originally Posted by hpbear101

Does that have any effect on seating depth of primer? Usually you would reduce rim thickness on the forward surface of the rim.

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If I’m lucky, I’ll get the chance to find out tonight when I try to prime some of these cases and load. I don’t have a tool to effectively reduce the forward surface of the rim.

In continuation, primers were still able to be seated “deep,” so no, this didn’t really impact seating of primers noticeably. 32 primed cases are now awaiting some test loads. Going to work up to 38gr of 3031 under 220gr 8mm Hornady spire points. I hear this can be a good, accurate load in these carbines.
Attachment 327544

Good deal. Post a thread on how they do :)